Felt conditioning apparatus for papermaking machine



July 16, 1968 E. A. KLINGLER ET AL FELT CONDITIONING APPARATUS FORPAPERMAKING MACHINE 2 Sheets-Sheet 1 Filed Feb. 4, 1965 INVENTORS EMILA. KLINGLER HEINZ FELDER ALFRED scuuazm' HANS JUD BY WM AGENTS July 16,1968 KUNGLER EIAL 3,393,123

FELT CONDITIONING APPARATUS FOR PAPERMAKING MACHINE Filed Feb. 4, 1965 2Sheets-Sheet 2 FIG.3 V 22 FIG.4

INVENTORS EMIL A. KLINGLER HEINZ FELDER ALFRED SCHUBERT NS JUD VQZZMMMAGENTS United States Patent 3,393,123 FELT CONDITIONING APPARATUS FORPAPERMAKING MACHINE Emil A. Klingler, Plochingen (N eckar), HeinzFelder, Dusseldorf-Benrath, Alfred Schubert, Stuttgart, and Hans Jud,Esslingen, Sulzgries, Germany, assignors to FeldmuhleAktiengesellschaft, Dusseldorf, Germany Filed Feb. 4, 1965, Ser. No.430,316 Claims priority, application Germany, Feb. 7, 1964,

9 Claims. 01. 162-274) ABSTRACT OF THE DISCLOSURE A felt conditioningapparatus for a paper-making machine in which two spaced elongated barsdefine a suction slot and are covered with sintered, parallelogramshapedaluminum oxide sections on their faces flanking the slot. The sinteredsections are attached to the bars in such a manner that they are capableof limited relative movement.

This invention relates to papermaking machinery, and particularly tofelt conditioning apparatus for use in the press section of aFourdrinier type papermaking machine.

It is conventional to pass a press felt over a suction box whichwithdraws absorbed liquid from the felt, thereby restoring thepermeability and absorbency of the felt for another pass between thepress rolls. Known felt suction boxes may consist of an axially slottedtube connected to a vacuum line. The felt passes approximatelytangentially over the slotted surface.

The known felt suction boxes are made of steel or bronze and aresubjected to relatively rapid wear by the moving felt. The edges of thesuction slot in the box are particularly rapidly worn, and the wornedges in turn attack the felt and are a prime source of feltdegradation. The frictional wear of the metallic materials ofconstruction conventionally employed is further accelerated by thechemical attack of acidic and other constituents in the white waterwhich is drawn from the felt.

We have found that the useful life of press felts can be greatlyincreased by making at least those portions of the associated feltsuction boxes which are in direct contact with the felts of sintered,dense, and very hard ceramic materials, and more specifically, tosupport facing plate sections of such material on a carrier structurewhich extends over the width of the felt to be conditioned, the severalsections being juxtaposed in the direction of felt width on either sideof the suction slot. The dimension of each individual section in thatdirection is but a fraction of the felt width, and the several sectionsare individually secured to the carrier structure in such a manner thatthey are capable of limited movement relative to each other.

Other features of the invention will become apparent to those skilled inthe art as the disclosure is made in the following detailed descriptionof preferred embodiments of the invention as illustrated in theaccompanying drawings in which:

FIG. 1 shows a felt suction box of the invention in elevational sectionon the line II in FIG. 2;

FIG. 2 illustrates the suction box of FIG. 1 in plan view;

FIG. 3 shows a modified felt suction box of the invention in afragmentary sectional view corresponding to that of FIG. 1; and

FIG. 4 shows yet another felt suction box of the invention in asectional view as in FIG. 1.

Referring now to the drawing in detail, and initially to FIG. 1, thereis seen the tubular cast iron shell 1 of a 3,393,123 Patented July 16,1968 'ice felt suction box. A drainage nipple 2 at the lowest point ofthe shell 1 is connected to a vacuum line when the suction box isoperated. As better seen in FIG. 2, a longitudinal slot 3 divides theflat top of the shell 1 so that two bar portions of the shell 1 extendalong the two sides of the slot 3.

Facing plate sections 4 cover the two bar portions of the shell 1practically over their entire length. A rib 5 projecting from theunderside of each plate section 4 engages one of two grooves in theshell 1 which extend over the full length of the shell on either side ofthe slot 3. The grooves are of shallow rectangular section. The exposedtop faces of the sections 4 have rounded longitudinal edges 6.

As seen in FIG. 2, the exposed faces of the plates, except for those ofthe longitudinally terminal plates 4', are of parallelogram shape. Theyare contiguously juxtaposed so that adjacent plates 4 or 4 formtherebetween a joint 7 which is obliquely inclined relative to thedirection of elongation of the shell 1, and relative to the direction offelt movement which is perpendicular to the length of the shell in theplane of FIG. 2.

The longitudinal ends of the slot 3 are provided in a conventionalmanner with bronze deckle blocks 8 having lateral ribs 9 slidablyreceived in longitudnailly elongated recesses in the walls of the slot3. Approximately prismatic facing plate sections 10 cover the deckleblocks 8 and have rounded edges at their exposed faces which are flushwith those of the sections 4. Screws 11 are provided for shifting theblocks 8 longitudinally in the slot 3 and for thereby varying theeffective length of the slot in a manner known in itself.

The facing plate sections 4, 4', 10 are secured to the supporting metalelements 1, 8 by an epoxy resin cement in a layer too thin to permitpictorial representation on the scale of FIG. 1. The engagement of theribs 5 on the plate sections 4, 4' with the grooves of the shell 1further secure the sections against the frictional stresses transmittedby the felt which moves over the exposed faces of the plate sections.

The sections 4, 4', 10 consist of sintered fairly pure aluminum oxideand are prepared by the method disclosed in more detail in the commonlyowned copending application Ser. No. 240,735, filed Nov. 28, 1962. Theycontain at least percent A1 0 and are shaped by molding and by firingthe green compacts at a temperature above 1000 C., and preferably above1200 C.

Although other dense and very hard ceramic materials such as siliconcarbide may be employed, and some of the advantages of this inventionmay be obtained thereby, facings of aluminum oxide are preferred andgive the most consistent long felt life While undergoing very littlewear. It is believed that aluminum oxide because of its chemicalstructure tends to retain the polar water molecules on its surface, andthus to maintain a water film at the interface of suction box and feltwhich acts as a lubricant.

Aluminum oxide and other ceramic products of the high hardness anddensity required for successfully carrying out this invention arebrittle. When facings extending over the full width of a press felt aremade of a unitary piece of ceramic material, the useful life of thefacing and of the cooperating felt is sharply reduced. The individualplate sections individually fastened to the supporting metallic carrierare capable of sufficient relative movement to prevent the transmissionof stresses other than compressive stresses to which sintered aluminumoxide and other suitable ceramic materials are highly reresistant.

Modern high-speed papermaking machines have effective widths of 20 feetand more. The individual facing plate sections employed with anelongated carrier structure extending over the full width of the machineshould not have dimensions of more than 24 inches in the direction ofcarrier elongation. Dimensions of 8 to 16 inches in that direction havebeen found to be most practical in almost all instances.

Aluminum oxide sections containing less than 95 percent Al O have asignificantly shorter useful life than those made of purer materialunder otherwise analogous conditions. It is difficult, if at allpossible, to produce sinte'red elements of a density approaching that ofcorundum from less pure raw materials. It is also believed that a verysmall grain size is not readily available in the presence of anexcessive amount of impurities, yet is desirable.

It is believed that sintered aluminum oxide bodies of a purity lowerthan 95 percent contain amorphous constituents which are concentrated atthe grain boundaries of the aluminum oxide and are more readily attackedby aqueous liquids so that individual crystals or grains may be loosenedand ultimately dislodged from an exposed surface. The resulting roughspot is a source of felt degradation and a starting point for furtherdestruction of the facing structure.

The surface finish of the aluminum oxide bodies affects felt life andthe durability of the facings. Rather surprisingly, exposed facingsurfaces of the highest possible polish do not produce the best results.It has been found most advantageous to finish the exposed surfaces insuch a manner that a layer on a level 0.5 micron below the envelopingsurface defined by the high points of the exposed face consists of notmore than 75 percent and not less than percent solid material, theremainder being occupied by voids.

Such a surface structure may be obtained directly by judicious selectionof starting materials and of suitable temperatures and times in thesintering process, but is more readily produced by grinding andpolishing an originally rougher surface. A secondary sintering operationor flame polishing also have been used successfully for the purpose. Theend point of the smoothing operation is determined by means of a knownsurface analyzer having a microscopic stylus which scans the surface.The movements of the stylus are transmitted to a recorder which plots acurve. Peaks of the curve represent the high points of the scannedsurface. A first line is drawn on the plot to connect these peaks, and asecond line parallel to the first line interesects areas under the curverepresenting solid material, and areas above the curve representingvoids. Smoothing of the surface is continued until the desired ratio ofsolid material and voids is obtained for all directions of stylusmovement on the exposed face.

A surface meeting the above requirements is formed during normaloperation of the felt suction box even when the surface finish of thefacing plate sections originally is rougher or smoother than the optimumrange. Quite surprisingly, the best surface finish is obtained quickerwhen the original finish was rougher than desired than with a facingthat is more highly polished than is necessary for meeting the abovelimitations. It is thought that the full retention of the aforementionedlubricating water film is predicated on the specified surface finish.When an aluminum oxide facing is provided with such a finish beforeinstallation, a costly break-in period causing damaged felts is avoided.

Metal and aluminum oxide faces that are adhesively secured to eachother, preferably by means of epoxy resin cement, are bonded morestrongly if roughened prior to cement application, and it is preferredto roughen the ribs 5, the underside of the facing section 10, the topface of the block 8, and as much of the corresponding surface portion ofthe shell 1 as is accessible prior to installing the facings 4, 4', '10by means of cement. Fastening methods other than cementing may beresorted to or may supplement cemented bonds, and modified felt suctionboxes of 4 the invention relying on such other fastening methods areshown in ele-vational section in FIGS. 3 and 4. When viewed in planView, they do not materially differ from what is shown in FIG. 2.

The felt suction box shown in FIG. 3 has a troughshaped lower part 13,partly broken away in FIG. 3, but fully shown in FIG. 4 and connected toa suction line. Two carrier bars 14 welded to the trough-shaped part 13extend inward of the trough opening to define therebetween a slot 3. Thelongitudinally terminal portions of the bars 14 are connected by a plate15 welded to the bars. Deckle blocks 16 are movably mounted in the slot3 in the known manner described with reference to FIG. 1. They arecovered with cemented aluminum oxide facings 17, whereas the carrierbars 14 are protected by respective facing plate sections 18, only oneof the numerous sections associated with each carrier bar beingillustrated.

A dovetail-shaped projection 19 at the underside of each facing platesection 18 engages a notch at the outer edge of the top face of eachcarrier bar 14. The notch has a fiat, horizontal wall which is incontact with the centrally recessed bottom face of the projection 19,and another wall which extends obliquely upward at an acute angle to thebottom wall. The oblique wall of the bar 14 conformingly engages acorresponding wall of the projection 19. The dimensions of theprojection 19 are such that there is no direct contact between any otherportion of the facing plate section 18 and the associated carrier bar'14.

The facing plate sections are urged horizontally inward of the notchesin the carrier bars 14 by two clamping devices each of which includesseveral screws 20 longitudinally spaced along each carrier bar 14 andthreadedly engaging the same. Only one screw 20 in each bar 14 isvisible in FIG. 3. The screws 20 pass through corresponding bores in anelongated clamping bar 21 one longitudinal edge of which engages an edgeportion of the carrier bar -14 and is pivoted on the bar 14 when thescrews 20 are tightened. A resilient spacer 22 is interposed between theother longitudinal edge of the clamping bar 21 and a side face of theprojection 19 of the facing plate section 18. When the screws 20 aretightened, the facing plate sections 18 are firmly anchored in thenotches of thecarrier bars 14. The spacers 22, which may be of cork,leather, rubber, or the like, distribute the pressure of the clampingbar 21 over the surface of the brittle ceramic facings.

The welded shell of the felt suction box shown in FIG. 4 consists of atrough 13- whose top is closed by two carrier bars 24, 24 except for aslot 3, the carrier bars being connected by Welded plates 15 at theirtwo ends, and deckle blocks 16 covered by cemented aluminum oxidefacings '17 being provided for adjusting the effective length of theslot 3 to the width of the felt, not itself shown, which travels overthe illustrated structure in the direction of the arrow.

The two sets of aluminum oxide facing plate sections 25 which cover thecarrier bars 24, 24' have ribs 26 on their undersides which engageconforming notches in the top faces of the associated carrier bars atthe leading edges thereof. The notch in the carrier bar 24 thus iscontiguous to the slot 3 whereas the notch of the carrier bar 24' isremote from the slot.

Stepped cylindrical bores 30 in the facing plate sections 25 arecoaxially aligned with threaded bores in the associated carrier bars 24,24. The stems of screws 27 threadedly engage the bores of the carrierbars, pass axially through the narrowest portion of the associated bore30, and carry screw heads which are received in a wider portion of thebore 30. The orifices of the bores 30 in the exposed face of the facingplate section 25 con stitute the widest axial portion of the bore. Theseveral sections of the bore 30 define shoulders therebetween. Aresilient washer 28 is interposed between one of the shoulders and theannular clamping face at the underside of the screw head. A plate shapedplug 2? of sintered aluminum oxide is adhesively fastened to the othershoulder and fills the orifice of the bore 30 flush with the ex posedface of the facing plate section.

The facing plate sections 25 are firmly secured to the supportingcarrier bars 24, 24"by the screws 27, but a layer of epoxy resin cementmay additionally be interposed between the sections and the bars. Thestresses transmitted to the suction box by the moving felt are largelyabsorbed by the abuttingly engaged vertical faces of the ribs 26 and ofthe associated carrier bars.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. 'It is therefore to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What we claim is:

1. In a felt conditioning apparatus for the press part of a papermakingmachine, in combination:

(a) two elongated carrier bar means spacedly juxtaposed;

(b) facing means on each of said carrier bar means and substantiallycompletely covering respective faces of the same,

(1) each facing means including a plurality of facing sectionsjuxtaposed in the direction of elongation of the associated bar means,

(2) each section essentially consisting of a hard,

dense, non-metallic, ceramic material,

(3) said two carrier bar means and the facing means thereon jointlydefining an elongated slot extending between said carrier bar means andbetween said facing means.

(c) fastening means securing each section to the associated carrier barmeans while permitting limited relative movement of the sectionsrelative to each other.

2. In an apparatus as set forth in claim 1, said material including atleast 95 percent aluminum oxide.

3. In an apparatus as set forth in claim 1, said sections consistingessentially of sintered aluminum oxide.

4. In an apparatus as set forth in claim 3, each section consisting ofnot more than per-cent and not less than 10 percent solids at a level0.5 micron below a surface defined by the high points of a face of saidplate section directed away from the associated carrier bar means.

5. In an apparatus as set fotrh in claim 3, said fastening meansincluding a clam-ping member secured to said associated carrier barmeans for movement toward said section.

6. In an apparatus as set forth in claim 5, said fastening means furtherincluding a resilient member contiguousl y interposed between saidclamping member and said section.

7. *In an apparatus as set forth in claim 5, said clamping member beinga screw having a threaded stern threadedly engaging said associatedcarrier bar means, and a head having an annular clamping face, saidsection being formed with a bore therethrough having an orifice in anexposed face of said section directed away from said carrier bar means,and having shoulder means in said bore for cooperation with saidclamping face, said head being received in said bore intermediate saidorifice and said shoulder means, and plug means in said orifice flushwith said exposed face for closing said orifice.

8. In an apparatus as set forth in claim 3, said fastening meansincluding a layer of epoxy resin cement interposed between said carrierbar means and each of said sections.

9. In an apparatus as set forth in claim 3, two juxtaposed sectionsdefining therebetween a joint obliquely inclined relative to thedirection of elongation of said carrier bar means.

References Cited UNITED STATES PATENTS 1,977,352 10/1934 Proulx 1623743,250,671 5/1966 Walker 162- 374 DONALL H. SYLVEST'ER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

